Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
In medical fields, a multi-gradation monochromatic image is used for medical diagnostic purposes, and the multi-gradation monochromatic image is generated by an image generating apparatus for medical use such as Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Computed Radiography (CR), Flat Panel Detector (FPD), and an ultrasonic diagnostic equipment or similar.
When utilizing the multi-gradation monochromatic image, for example, displaying the multi-gradation monochromatic image in a display device such as Cathode Ray Tube (CRT), or printing the displayed multi-gradation monochromatic image on a paper sheet by an output device such as printers, are performed.
In this use of the multi-gradation monochromatic image, because of such purpose, it is important to maintain gradation reproducibility in the display device and the output device.
Especially, the output device such as the printers is likely to change in a characteristic of each portion by secular changes, and therefore, maintaining the gradation reproducibility is performed by a calibration generally.
However, when the characteristic of each portion of the output device significantly changes, maintaining the gradation reproducibility even with the calibration becomes difficult and a reproducible gradation range (number of gradation levels) may decrease. In this case, the detection of such as a tumor, which has been detectable, may also not be able to be performed because a gradation outside the reduced gradation range cannot be accurately reproduced on the paper sheet.
The gradation range reproducible on the paper sheet is lower than that of an image display device of an information processor. Accordingly, similarly to the above-described, the multi-gradation monochromatic image might not be able to be accurately reproduced on the paper sheet even if the gradation reproducibility of the output device is maintained by the calibration.
On the other hand, recently, there has been an increase in cases of employing the various models available from a plurality of manufacturers as the output device of a medical image forming system. The gradation reproducibility may differ among such different output devices.
Accordingly, the gradation might be inconsistently reproduced depending on the output device even if the identical multi-gradation monochromatic image is provided.
In response to this, there is a known technique to ensure consistency in visibility among the devices by defining a contrast sensitivity of a grayscale image with using Grayscale Standard Display Function (GSDF) in the standard of Digital Imaging and Communications in Medicine (DICOM).
In this known technique, the visibility among the output devices can be controlled by adjusting a luminance range. However, adjusting it to the lower degree of the luminance range may cause the deterioration of the gradation reproducibility in some output devices.
There is a method for enhancing a gradation degree in some optical density regions. This case may cause loss of an image total balance, and the deterioration of the gradation reproducibility may occur.